JPH0376447A - Privacy call equipment - Google Patents

Abstract

PURPOSE:To sufficiently ensure the secrecy of communication by providing a conversion circuit revising a setting value of a cryptographic key from a cryptographic key setting means so as to revise the cryptographic key differently from each communication thereby revising the setting of the cryptographic key without disturbing the user. CONSTITUTION:A cryptographic key from a cryptographic key setting means 5 is fed to a microcomputer 6 via a cryptographic key conversion circuit 17 comprising an arithmetic circuit. A data of number of times of communication is fed to the conversion circuit 17 from the microcomputer 6 and the cryptographic key supplied from the cryptographic key setting means 5 is revised to be different from each communication. Thus, it is not required to enter a decoding key at a receiver side and a sender side freely revises the cryptographic key. Then the cryptographic key from the cryptographic key setting means 5 is revised by the conversion circuit 17 different from each communication. Thus, the secrecy of the communication is sufficiently secured without disturbing the user.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is directed to a secret communication device suitable for use in, for example, wired or wireless digital communications.

[Prior Art] In communication 1g, if the communication content is confidential, it is necessary to perform confidential communication. In this case, on the sending side, normal data (plaintext) is encrypted, and this encrypted data (ciphertext) is transmitted. Then, on the receiving side, this ciphertext is decrypted into plaintext.

FIG. 5 shows a conventional confidential communication device.

In the figure, on the transmitting side, plaintext is supplied to an encryption circuit 13 and converted into ciphertext according to an encryption key. The ciphertext from the encryption circuit 13 is supplied to the receiving side via a wired or wireless communication section. Also, on the receiving side, the ciphertext is supplied to the decryption circuit 14 and decrypted l! 16 into plaintext.

[According to the example of FIG. 5, the sender and receiver need to possess, for example, the same key for encryption and decryption. Therefore, the sending side could not freely change the encryption key. However, to ensure the confidentiality of communications,
It is necessary to change the encryption key frequently.

Therefore, the applicant of the present invention has previously proposed a secret device that can freely change the encryption key (Japanese Patent Application No. 1-70200).This secret device will be explained below.

21st! I is a block diagram of the transmitting side.

In the figure, 20 is a pseudo-random signal generation circuit, and this pseudo-random signal generation circuit 20 is a switch for selecting the cascade connection stage 1 of the six stages of shift registers 5RI-9R6 and the feedback path of the cascade connection stage 1. It is composed of circuit 2.

The loading and shifting states of the shift registers SRI to SR6 of the cascade connection stage I are controlled by a control signal S/L from the microcomputer 6, which is a control means. When the control signal S/L is in the load state, the shift register SRI
~SRB contains initial value data D! from the microcomputer 6! ~D6 is loaded. Incidentally, these shift registers 5RI-5R6 are made to operate in cycles with the clock CK.

The switching circuit 2 is composed of various gates and inverters. That is, the AND gate 21 is supplied with the output signal of the shift register SR5 and also with the control data D7 from the microcomputer 6. Further, the output signal of the shift register SR1 is supplied to the AND gate 23, and the control data D7 is supplied to the inverter 2.
2. And these and gate 2
The output signals of 1 and 23 are supplied to an OR gate 24. Therefore, depending on whether the control data D7 is at a high level or a low level, the shift register S is output from the OR gate 24.
The output signal of RI or SR5 is output.

Further, the exclusive OR gate 25 is supplied with the output signal of the OR gate 24, and the shift register S
The output signal of R6 is provided. The output signal of this exclusive OR gate 25 is transmitted to the shift register SR.
Returned to I. Therefore, shift register SRI~
When SR6 performs a shift operation, shift register SR6
The initial value data Dl-D6 and a pseudo-random signal according to the selection of the switching circuit 2 are outputted from the circuit.

Further, 5 is a code II setting means, and this code key setting means 5 is composed of seven connection switches for selecting a high level or a low level. In this case, one end of these seven connection switches is connected to the terminal Rm, and the other end is connected to the terminals Pil to Pi7 of the microcomputer 6.

Further, 3 is a storage circuit composed of, for example, a ROM (read only memory), and this storage circuit 3 stores initial value data DI-Da supplied to the shift registers SRI to SR6 of the cascade connection stage 1, and a switching circuit 2. A plurality of sets of control data D7 supplied to the control data D7 are stored.

In this case, the address signal corresponding to the encryption key set by the encryption key setting means 5 is sent from the microcomputer 6 to the storage time W.
i3, and the corresponding initial value data DI to D6 and control data D7 are read out. The initial value data D1 to D6 and #1m data D7 are supplied to the shift registers SRI to SR6 and the switching circuit 2 via the terminals Pot to Po7 of the microcomputer 6.
As a result, the pseudo random signal generation circuit 20 is initialized.

Further, the address signal from the microcomputer 6 is converted into a serial signal by the parallel/serial conversion circuit 4 and output.

Further, 7 is an encryption circuit composed of an exclusive-or gate, and this encryption circuit 7 receives a pseudo-random signal from a pseudo-random signal generation circuit 20 and serial data from a data generation means (not shown). (eg, audio data) and the serial data is encrypted.

Further, 8 is a data/control signal switching circuit, and this switching circuit N8 receives an address signal output from the conversion circuit 4, encrypted data output from the encryption circuit 7, and a synchronization signal from the synchronization signal generation circuit 9. is supplied. Under the control of the microcomputer 6, these signals are switched in synchronization with the clock CK and output to a wired or wireless communication line. FIG. 4 shows an example of the structure of the communication signal.

In this way, on the transmitting side, data is encrypted according to the encryption key setting by the encryption key setting means 5, and is output to the communication line together with the synchronization signal and address signal.

FIG. 3 is a block diagram of the receiving side. In FIG. 3, parts corresponding to those in FIG. 2 are designated by the same reference numerals.

In the figure, a signal from a communication line is supplied to a synchronization signal detection circuit 12 via a data/control signal switching circuit 8, and a synchronization signal (
(see FIG. 4) is supplied to the microcomputer 6.

Further, the switching circuit 8 is supplied with a control signal and a clock from the microcomputer 6 in accordance with the synchronization signal. Then, the address signal included in the signal from the communication line is passed through the switching circuit 8 to the serial/parallel conversion circuit 1.
After being converted into a parallel signal at 0, the signal is supplied to the microcomputer 6. This address signal is then supplied from the microcomputer 6 to the memory circuit 3, and the corresponding initial value data D1-D6 and control data D7 are read out. The initial value data DI~D6 and the control data D7 are sent to the terminals Pol~ of the microcomputer 6.
It is supplied to shift registers SR1 to SR6 and switching circuit 2 via Po7.

As a result, the pseudo random signal generation circuit 20 is initialized.

In this case, the storage contents of the storage circuits 3 on the reception side and the transmission side are the same, and the pseudorandom signal generation circuits 20 on the reception side and the transmission side have the same configuration. , a pseudo-random signal similar to that on the transmitter side is generated.

Further, 11 is a decoding circuit composed of an exclusive OR gate. The decryption circuit 11 is supplied with the pseudorandom signal from the pseudorandom signal generation circuit 20 and the encrypted data from the switching circuit 8, and the encrypted data is decrypted and output.

In this way, according to the secret communication device shown in FIGS. 2 and 3, there is no need to manually enter a decryption key on the receiving side, and the encryption key can be freely changed on the transmitting side.

However, the encryption key is set by the user, and unless the user changes the setting value, the pseudo-random signal generating circuit 20 always generates the same pseudo-random signal for encryption. Therefore, − degrees,
If it is decrypted by a third party, the secrecy of the communication cannot be ensured.

Therefore, in this invention, without bothering the user,
To provide a confidential communication device that can sufficiently ensure the secrecy of communication.

[Means for Solving the Problems] A confidential communication device according to the present invention is configured as follows. That is, on the transmitting side, there is a first pseudo-random signal generation circuit and a cipher l! for setting an encryption key. a setting means, a conversion circuit for changing the setting value of the encryption key, a first storage circuit that stores initial setting data of the pseudo-random signal generation circuit, and a first a first control means that reads initial setting data from the memory circuit and sets the first pseudo-random signal generation circuit; and an encryption circuit that encrypts the human data using the output signal of the first pseudo-random signal generation circuit. and will be provided. Then, the output data and address signal of the encryption circuit are transmitted.

Further, on the receiving side, there is provided a second pseudo-random signal generation circuit having the same configuration as the first pseudo-random signal generation circuit, a second storage circuit that stores the same contents as the first storage circuit, and a second storage circuit that stores the same contents as the first storage circuit. a second control means that reads initial setting data from the second storage circuit according to the address signal and sets the second pseudo-random signal generation circuit; and decodes the received data according to the output signal of the second pseudo-random signal generation circuit. A decoding circuit is provided.

[Operation] In the above-described configuration, a conversion circuit 17 is provided for changing the setting value of the encryption key from the encryption key setting means 5. In this conversion circuit 17, the encryption key is changed differently, for example, for communication. Therefore, the setting of the encryption key can be changed without bothering the user, and communication secrecy can be sufficiently ensured. [Embodiment] Hereinafter, with reference to FIG. 1, an embodiment of the present invention will be described. explain. In FIG. 1, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In this example, the encryption key from the encryption 1 setting means 5 is supplied to the microcomputer 6 via the encryption key conversion circuit 17 composed of an arithmetic circuit. The conversion circuit 17 is supplied with data on the number of communications from the microcomputer 6, and the encryption key supplied from the encryption key setting means 5 is changed for each communication.

Examples of arithmetic processing for such changes range from simple ones such as adding "l" for each communication to complex ones such as scrambling using a PN generation circuit, multiplication, division, and various other operations. Conceivable.

This example is constructed as described above, and other parts are constructed in the same manner as the example in FIG. Note that the receiving side is configured in the same manner as the example in FIG.

According to this example, there is no need to manually generate the decryption key on the receiving side.
The sender can freely change the encryption key. Then, the encryption key from the encryption key setting means 5 is changed by the conversion circuit 17 to be different for each communication. Therefore, communication secrecy can be ensured sufficiently without bothering the user.

In the above embodiment, the number of stages of the shift register in the cascade connection stage l is six, but it can be any number of stages. Further, the signal fed back to the shift register SRI is not limited to the above-mentioned embodiments, and can be the output of any shift register.

[Effects of the Invention] As explained above, according to the present invention, there is no need to manually create a decryption key on the receiving side, the sending side can freely change the encryption key, and it is possible to change the encryption key from the encryption key setting means. Since the encryption key is changed by a conversion circuit, for example, to be different for each communication, it is possible to sufficiently ensure the secrecy of communication without bothering the user.

[Brief explanation of drawings]

11th! I is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of the transmission side of the privacy device, FIG. 3 is a block diagram of the reception side of the privacy device, and FIG. 4 is a diagram showing the configuration of a communication signal. , FIG. 5 is a block diagram of a conventional secret communication device. 3 ◆ 4 ・ 5 ・ 6 ◆ 7 ・ 8 ◆ 9 ・ 0 e 1 l ・ 12 ・ 17 ・ ・Memory circuit e Parallel/serial conversion circuit ・Encryption key setting means ◆Microcomputer ・Encryption circuit ・Data/control signal switching Circuit ◆ Synchronous signal generation circuit, serial/parallel conversion circuit, decoding circuit, synchronous signal detection circuit, encryption key conversion circuit 20 ◆ ・Pseudo-random signal generation circuit

Claims (1)

[Claims] (1) The transmitting side includes a first pseudo-random signal generation circuit, an encryption key setting means for setting an encryption key, a conversion circuit for changing the setting value of the encryption key, and an initial stage of the pseudo-random signal generation circuit. A first storage circuit that stores setting data, and an address signal corresponding to the encryption key from the conversion circuit to read the initial setting data from the first storage circuit and set the first pseudo-random signal generation circuit. and an encryption circuit for encrypting input data using the output signal of the first pseudo-random signal generation circuit, the output data of the encryption circuit and the address signal being transmitted; On the receiving side, there is a second pseudo-random signal generating circuit having the same configuration as the first pseudo-random signal generating circuit.
a pseudo-random signal generating circuit; a second memory circuit that stores the same contents as the first memory circuit; and a second memory circuit that reads the initial setting data from the second memory circuit in response to the received address signal, A secret communication device comprising: second control means for setting the pseudo-random signal generation circuit; and a decoding circuit for decoding received data using the output signal of the second pseudo-random signal generation circuit. .